For the haziest of reasons, there is a near taboo on the portrayal of adult brothers and sisters in film

In When Harry Met Sally, Billy Crystal and Meg Ryan famously argued over whether men and women could be friends without one of them wanting to have sex with the other. When I first saw the film 11 years ago, I found it funny, entertaining and a good conversation piece, but I couldn’t help thinking that Crystal and Ryan — neither of whom seemed to have any family beyond their fellow single New Yorkers — had overlooked something. I could certainly think of a few women in my own life for whom this was a non-issue, and one of them was sitting right next to me in the theatre. I refer, of course, to my sister.